What Causes Recurring Nausea, Cramping, Sulphur Flatulence And Diarrhea?

YEs I have had this problem for over 10 years. I have had numerous scans, tests, gastroscopy, colonoscopy, biopsies, faeces tests- everything! It starts with nausea, sulphur foul tasting burps then bad nausea and cramping for hours before either vomiting or diarrhoea. Then that lasts for about 24 hours. It can come back in a couple of weeks or days...or months. Sometimes i don t suffer for a couple of years. I have no idea what to do and will take anything or do anything to get rid of this!!!!